S32K388 RMII Reference Clock

[javivalero]

Good Morning, 

I have an issue with the S32K388 on the RMII interface of a custom board. 

The S32K388 is setup as the MAC and is connected to a PHY. 

The issue is related with 50MHz reference clock because I want to generate it internally and send it to the PHY using the gmac1_mii_rmii_rgmii_tx_clk pin. All the examples that I have found use an external crystal oscillator (ex. S32K324 MII mode - NXP Community) but I think it is not necessarily required after reading this in the RM:

I wasn't able to find in the RM how achieve it. 

Any help would be appreciated!

Thanks in advance!

[PavelL · Accepted solution]

Hi @javivalero ,

In theory, it is possible to generate the clock reference from the internal PLL and connect it to the gmac1_mii_rmii_rgmii_tx_clk (PTC1) pin. However this was thought for RGMII mode, not RMII.

Best regards,

Pavel

[PavelL]

Hi @javivalero ,

what PHY are you using? Could you shared schematic of your board?

Best regards,

Pavel